Method for monitoring film thickness of optical filter

Abstract

The present invention discloses a monitoring method of optical filter film thickness. Said method includes the following steps: firstly, calculating spectral curve of every monitoring film using central wavelength lambda O as monitoring wavelength; calculating series spectral curve using out-of-centre wavelength as monitoring wavelength; then using conventional extreme indirect monitoring method to plate optical film on substrate; testing the spectral curve of plated filter; comparing the tested spectral curve with analogously-calculated spectral curves to find out most similar spectral curve in the calculated spectral curves, regulating monitoring wavelength and preparing new filter again, repeating the above-mentioned steps until the waveform and transmittance or reflectance indexes spectral curve of filter are reached to indexes of designed requirements.

Description

Technical field [0001] The invention relates to the field of optical films, in particular to a method for monitoring the film thickness of an optical filter. technical background [0002] The optical filter is composed of a substrate and a vacuum evaporation optical film system on the substrate. When the optical film is deposited, the reflected and transmitted light will change due to the change of the thickness of the film. Therefore, it is most appropriate to use the change of the optical signal to control the change of the thickness of the film. The commonly used optical film thickness monitoring methods are: the visual method to directly observe the color change of the film; the wavelength modulation method to measure the derivative change of the transmittance or reflectance with respect to the wavelength; to measure the extreme value change of the transmittance or reflectance of the film. Value method. [0003] The visual method uses the human eye as a receiver to visually o...

AI Technical Summary

Problems solved by technology

Its disadvantages are: when the film is coated to a thicker thickness, the monitoring optical signal will be deformed; the error caused by the change of the coating state cannot be easily compensated

The disadvantage is that when the sample to be plated is deposited to a certain thickness and a new monitoring sheet is replaced, there is a significant difference between the thickness of the film layer deposited on the sample to be plated and the film layer deposited on a new monitoring sheet at the same time. The difference; the extreme value control accuracy of each layer is low

[0009] The semi-direct control method is between the two. It directly controls the film thickness of the entire coating process on the monitoring sheet coated with pre-coating, and there is also the problem of control accuracy.

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